Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
import math
import sys
from collections import deque
import copy
def mi() : return map(int,input().split())
a,b=mi()
l=[list(input()) for _ in range(a)]
count=0
for i in range(a):
  for _ in range(b):
    if l[i][_]==".":
      count+=1
l[0][0]=1
q=deque([[0,0]])
while q:
  x,y=q.popleft()
  if x==a-1 and y==b-1:
    print(count-l[x][y])
    sys.exit()
  for e,f in [[0,1],[0,-1],[1,0],[-1,0]]:
    if 0<=x+e<a and 0<=y+f<b and l[x+e][f+y]==".":
      l[x+e][f+y]=l[x][y]+1
      q.append([x+e,y+f])
print(-1)